Web interface and Sign Up:

Use decred.org. For development, please use the same name you use on github.
Once logged in, join the Cryptopower room by clicking on Explore on the top left.

Mobile apps:

Android chat and iOS chat can be configured with the decred.org home server.

Matrix users:

If you already have a matrix account, get a list of our rooms in your matrix client by selecting
Explore → Matrix Rooms → Add a new server → decred.org